On the end of my white board I have a chart with students names and two columns, one marked yes and the other no. I have magnets (staples for $2.99). At the end of the day I explain the homework and make sure they understand it. If they do they can leave and place their magnet under yes. If not I explain it to them. In the morning I collect homework and if they have their homework I move their magnet by their name. If they don't I place it in the "no" column. Any no marks results in doing homework during recess. The student also has to sit out why we check homework (I don't grade homework).